Cephalometric comparison of mandibular growth in Brazilian children with Class II malocclusion and normal occlusion during the growth stages determined by the cervical vertebrae maturation

ABSTRACT Objective: This study compared mandibular growth in children, aged 7 to 12 years, with Class II malocclusion and normal occlusion, between the following stages of cervical vertebrae maturation: initiation (I), acceleration (A), transition (T). Material and Methods: A total of 148 lateral cephalograms (78 males, 70 females) of Class II malocclusion patients, and 60 lateral cephalograms (30 males, 30 females) of normal occlusion patients were included. The following linear cephalometric measurements were performed: Co-Gn (effective mandibular length), Co-Go (ramus height), and Go-Gn (length of mandibular body). Mean values of increments between stages (I-A, A-T, I-T) were obtained for each group and gender. Results were compared using the Student t-test, and a significance level of 0.05% was adopted. Results: Females group: A-T interval presented a greater increment in Co-Go in the Class II group, which was not significant for the I-T interval, with numerically smaller increments in Co-Gn and Go-Gn, without statistical significance. Males group: intervals I-A, A-T and I-T showed numerically smaller growth increments in the Class II group, with statistical significance for Co-Gn in I-A (p=0.001) and I-T (p=0.003). Comparing genders of the Class II group, Co-Go was higher in males (p=0.002) and I-T interval (p=0.031). In the Normal Occlusion group, the male gender had the greatest Co-Gn (p=0.038) for the I-A interval. In A-T and I-T, Co-Go in males was higher, with statistical significance (p=0.000 and p=0.002, respectively). Conclusion: Growth phenomenon affects the mandibular dimensions regardless of the character of the malocclusion, with a tendency to be smaller in the presence of Class II malocclusion.


INTRODUCTION
Knowledge regarding the growth phenomenon is important in Orthodontics, especially for Class II malocclusion treatment, as the choice of a therapeutic approach to be used during maxillomandibular growth must be based on the patient's skeletal maturation stage, since the success or failure of orthodontic treatment can be directly related to craniofacial growth and development. 1 Class II is the most frequent malocclusion in the orthodontist's office, 2,3 its particular characteristics are investigated in an attempt to identify the main cause responsible for the dysplasia, which can range from mandibular deficiency to maxillary protrusion, 4 and thus, studies have reported that mandibular retrusion is the main cause of this malocclusion, with some exceptions. 5me studies in the literature [6][7][8][9][10] described the amount of annual growth increments that occur in children with normal occlusion, favoring the diagnosis and orthodontic treatment.
However, few studies 8,11,12 have evaluated craniofacial growth in Class II malocclusion by comparing it with a normal occlusion control group, thus demonstrating the growth alterations that occur in Class II in the pubertal growth stage, which is the ideal stage for an orthodontic treatment with better prognosis.A systematic review concluded that orthodontic Class II treatment before the puberal growth spurt does not efficiently correct the skeletal problem, and the facial profile may not sufficiently improved. 139][20] The CVM method has been used to predict when the maximum rate of facial growth occurs in Class II malocclusion. 12,20-22Some studies [19][20][21][22] have correlated the period of greatest changes in cephalometric variables with the morphology of cervical vertebrae.However, these studies differed from the original method by Lampalski 18 modified by Hassel and Farman 23

and described by McNamara Jr and
Franchi 24 in details, based on the almost 20 years of experience in staging cervical vertebrae, in an article prepared as a "user's guide", in an attempt to help the professional using this approach in everyday clinical practice Thus, the aim of the present study was to evaluate the growth increments occurring in untreated mandibular Class II malocclusion using serial cephalograms, identifying the pubertal growth spurt between the stages of greater growth expectation (initiation, acceleration and transition), using the method by Lampalski 18 modified by Hassel and Farman, 23    The Class II group had a retrusive character of the mandible, in relation to the Normal Occlusion group (p=0.000).The power of the test was performed for the Co-Gn measure, considering the effect size equal to 1 and the significance level of 5%, with a mean for males and females of 84.5%.The ages of patients in each stage are shown in Table 2.All lateral cephalograms showed good quality, allowing the assessment of anatomical structures and cervical vertebrae (C2, C3 and C4), to score the skeletal maturation, using the method of Hassel and Farman, 23         The sample consisted of three subgroups categorized according to CVM method. 24In this study, the sample was grouped according to three periods: prepubertal growth spurt (I-A), including subjects in the interval between CS1 and CS2 stages; pubertal growth spurt (A-T), including subjects in the interval between CS3 and CS4 stages; and I-T, to evaluate what happened between I and T phases.
The cephalograms were digitized using an Numonics AccuGrid A30TL digitizing table, connected to a microcomputer with a P3 700MHz Intel processor, to obtain the cephalometric measurements.The tracing and digitalization of points were performed by a single examiner, using the OrthoLateral pattern of the DentoFacial Planner 7.02 program, to obtain the measurements.Correction of the magnification factor (6% for the sample radiographs obtained up to 1995 and 9.8% for those obtained after 1996) was performed by the program.

METHOD ERROR
To assess the intra-examiner error, forty-five lateral cephalograms were randomly selected, 26 which were traced and digitized by the same researcher at an initial time (T1) and repeated after a 30-day interval (T2), according to Midtgard, Bjork and Linder-Aronson. 27 evaluate the systematic error as recommended by Houston, 28 a paired t-test was used with a p-value <0.05.Application of the formula proposed by Dahlberg 29 allowed estimating the order of random errors magnitude.To assess the reliability of the CVM stages, data obtained at T1 and T2 were analyzed by Kappa agreement coefficient for intra-examiner evaluation, which, according to Landis and Koch, 30 varies from -1 to 1.
The compatibility of groups regarding the proportion of genders, CVM stages, and ages was evaluated using the chi-square test.

STATISTICAL ANALYSIS
The amount of increments between stages (I-A, A-T and I-T) in males and females was evaluated, thus obtaining the means and standard deviations for each variable, as well as the result of the t-test applied between the means, to identify statistically significant differences between the groups.Chi-square test was used to evaluated the compatibility of groups.
All statistical analyses were conducted using the Statistica software (Statistica for Windows, release 6.0,Copyright StatSoft, Inc), and results with p<0.05 were considered significant.

RESULTS
No systematic errors were found, and random errors were considered acceptable, all of which were below 1mm for linear measurements (Co-Go=0.763mm;Co-Gn=0.604mm; Co-Gn=0.052mm).The Kappa coefficient was used to assess the intra-examiner agreement regarding the cervical vertebrae maturation stage (0.91=almost perfect), expressing high precision of the methodology adopted.The present study compared the mandibular growth between individuals with Class II and normal occlusion, using the first three CVM stages (considered the ones with higher growth expectations) of the Hassel and Farman 23 method (modified by Lamparski and Nanda, 31 and described by McNamara Jr and Franchi 24 ).
The results of the comparison between the two groups for males and females at each CVM stage are shown in Table 3.
In female gender, Co-Gn and Go-Gn were not significantly different between groups, while Co-Go was significantly different for Class II group.In the male group and stage I, the effective mandibular length (Co-Gn) and the mandibular ramus height (Co-Go) showed statistically significant differences between groups.Contrary to stage I, there was no significant difference for Co-Gn and Co-Go in stage A: male Normal Occlusion group showed a gain of 7.47mm in the effective mandibular length (Co-Gn), while the male Class II group obtained 3.63mm; the ramus height (Co-Go) in the male Normal Occlusion group had a gain of 3.14mm, while the male Class II group had only 1.68mm.For Go-Gn, the gain in the Normal Occlusion group was 4.84mm, while in the Class II group it was only 2.88mm.
In stage T, the Class II male group presented an effective mandibular length (Co-Gn = 108.40mm)numerically smaller than that of Normal Occlusion group (Co-Gn = 109.73mm),but without significant differences (p = 0.488).This occurred due to the greater increment obtained in the male Normal Occlusion group (7.33mm) than in the Class II group (5.07mm).The Co-Go and Go-Gn measurements showed no difference between the groups, and greater increments were also observed in the Normal Occlusion group.To evaluate whether there was significant difference between the increments that occurred between stages (I-A, A-T, I-T), the amount of mandibular increments from Initiation to Acceleration (I-A), Acceleration to Transition (A-T) and Initiation to Transition (I-T) in females and males is shown in Table 4, with all variables representing mandibular dimensions being influenced by growth in the three studied stages.
Between female groups at I-A stage, the Class II group showed smaller amounts of growth increments in the variables that represent the mandibular dimensions; however, without significant difference.For the A-T stage, the amounts of growth increments in the effective length of the mandible (Co-Gn) and ramus body (Go-Gn) were smaller in the Class II group, still without significant difference; while the increment achieved in the mandibular height (Co-Go) was higher and statistically significant for the Class II group.For the I-T interval, growth increments occurred in the three studied variables, mainly in the Normal Occlusion group, but without significant difference, showing that the growth phenomenon occurred in all individuals in the studied stages, regardless of the malocclusion present.
Between male groups for the I-A interval, the Class II group showed smaller amounts of growth increments in the variables that represent the ramus height (Co-Go) and the mandibular body length (Go-Gn), but without significant differences; while the effective mandibular length (Co-Gn) was statistically greater (p=0.001) in the Normal Occlusion group.For the A-T interval, all the increments that occurred in the mandibular variables remained numerically smaller in the Class II group, but without significant differences.For the I-T interval, the amount of growth increment in effective mandibular length (Co-Gn) was statistically smaller (p=0.003) in the Class II group, while in ramus height (Co-Go) and mandibular body length (Go-Gn), there were no statistically significant differences.

Table 4: Growth increments in mandibular dimensions between CVM stages (I-A, A-T and I-T)
for the female and male groups, and the comparison between groups (t-test).

Compatibility regarding gender ratio was tested between
Class II and Normal Occlusion groups (Table 2), and, according to several studies, growth is more advanced in females. 9,32e maturation levels increase earlier in women, 33 and indexes of maturation might provide a rough assessment of a patient's current state of development.
The selected age ranges were wide enough to ensure including the growth peak in the sample, even tough maturation levels increase earlier in women, 9 but only the Acceleration phase in the Class II group was statistically significant.
There was intergroup compatibility regarding the stages of skeletal maturation, ensuring the similarity between the growth stages between Class II and Normal Occlusion groups.
The Normal Occlusion sample in this study was not evaluated regarding growth type.d indicated that the intraobserver and interobserver agreements were substantial, it can be concluded that the current CVM classification method is reproducible and reliable.
The increments of the mandibular dimensions are distributed over a wide range of chronological age intervals, which makes it unreliable to depend on chronological age to assess a patient's skeletal growth stage. 35e Class II group (Table 4) showed smaller amounts of growth increments in the variables that represent the mandibular dimensions in I-A interval; however, without statistical significance.This is corroborated by Bishara et al 36 and Bishara,37 who also found no significant difference in mandibular growth between individuals with Class II malocclusion and Normal Stahl et al, 12 except for Co-Gn in the normal occlusion male group, which was statistically significant (p=0.001)-the mean of this increment was between 3mm and 7mm.
At A-T interval, the increment in the mandibular height (Co-Go = In males group, the increments in Normal Occlusion group ranged from 4mm to 14mm, being higher in the Normal Occlusion group, and with statistical significance in I-A and I-T intervals, showing that the stages A and T are almost always involved with bigger increments, which is in accordance to Montasser, 9 who also showed that the growth spurt peak almost always occurs either in the CVM2-CVM3 or the CVM3-CVM4 intervals.
The mandibular growth deficiency in Class II subjects is significant not only in the growth spurt, but is also maintained at postpubertal observations. 12Although the current findings are based on cross-sectional data, the possibility that Class II dentoskeletal malocclusion does not have a tendency to self-correct with growth should not be neglected. 38a

CONCLUSIONS
In females, there was a tendency for greater growth increments for the Normal Occlusion group at I-A interval.At A-T interval, Co-Go increment was significantly greater for the Class II group.At I-T interval, the increment values tended to remain numerically higher for the Normal Occlusion group, but without significant differences.
The male gender showed numerically greater increments for all mandibular growth measurements in the Normal Occlusion group, with statistically significant differences for the effective mandibular length at I-A and I-T intervals.
Although the present study has evaluated CVM stages I to T in a 7 to 12 years old sample, it is suggested that future studies be carried out evaluating up to the last CVM stage, with a sample presenting a higher age range, to evaluate whether the phenomenon affects the mandibular dimensions regardless of the malocclusion character, with a tendency to be smaller in presence of Class II malocclusion in all CVM stages, and considering the possibility that Class II dentoskeletal malocclusion does not have a tendency to self-correct with growth. 38a

Silva 3 Dental
FLBS, Conti ACCF, Fernandes TMF, Araújo PPB, Pinzan A -Cephalometric comparison of mandibular growth in Brazilian children with Class II malocclusion and normal occlusion during the growth stages determined by the cervical vertebrae maturation

Silva 5 Dental
FLBS, Conti ACCF, Fernandes TMF, Araújo PPB, Pinzan A -Cephalometric comparison of mandibular growth in Brazilian children with Class II malocclusion and normal occlusion during the growth stages determined by the cervical vertebrae maturation n = number of patients.CVM = cervical vertebrae maturation (I = initiation, A = acceleration, T = transition).

Silva
FLBS, Conti ACCF, Fernandes TMF, Araújo PPB, Pinzan A -Cephalometric comparison of mandibular growth in Brazilian children with Class II malocclusion and normal occlusion during the growth stages determined by the cervical vertebrae maturation Dental Press J Orthod.2023;28(5):e232358

Figure 1 :
Figure 1: Initiation: lower edges of C2, C3 and C4 are flattened or flat, and upper edges are tapered from posterior to anterior.At this stage, pubertal growth and development is initiating, with an expectation of growth of 80% to 100%.

Figure 2 :
Figure 2: Acceleration: lower edges of C2 and C3 begin to show concavities, but the edge of C4 is still flat or flattened.The vertebral bodies of C3 and C4 are approximately rectangular in shape.At this stage, pubertal growth and development have already started, with an expectation of growth of 65% to 85%.

Figure 3 :
Figure 3: Transition: C2 and C3 present with distinct concavities on their lower borders, and C4 presents with onset of concavity on the lower border.The vertebral bodies of C3 and C4 are rectangular in shape.Pubertal growth is slowing down, but still has 25% to 65% of growth expectation.

Figure 4 :
Figure 4: Lines and planes used in this study.

SilvaFLBS, 15 Dental
Conti ACCF, Fernandes TMF, Araújo PPB, Pinzan A -Cephalometric comparison of mandibular growth in Brazilian children with Class II malocclusion and normal occlusion during the growth stages determined by the cervical vertebrae maturation

20 Dental
FLBS, Conti ACCF, Fernandes TMF, Araújo PPB, Pinzan A -Cephalometric comparison of mandibular growth in Brazilian children with Class II malocclusion and normal occlusion during the growth stages determined by the cervical vertebrae maturation

21 DentalFLBS»»
photographs.»The authors report no commercial, proprietary or financial interest in the products or companies described in this article.

Table 1 :
I-A, A-T and I-T intervals, for male and female genders in both groups.

Table 2 :
Descriptive statistics for ages (in years) in the CMV stages (t-test) , for both groups.

Silva FLBS, Conti ACCF, Fernandes TMF, Araújo PPB, Pinzan A -Cephalometric comparison of mandibular growth in Brazilian children with Class II malocclusion and normal occlusion during the growth stages determined by the cervical vertebrae maturation 11 Dental
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Silva FLBS, Conti ACCF, Fernandes TMF, Araújo PPB, Pinzan A -Cephalometric comparison of mandibular growth in Brazilian children with Class II malocclusion and normal occlusion during the growth stages determined by the cervical vertebrae maturation 12 Dental
Detailed distributions of CVM stages for both sexes by chronological age are represented in Table2, showing precocity of the stages in female patients.

Silva FLBS, Conti ACCF, Fernandes TMF, Araújo PPB, Pinzan A -Cephalometric comparison of mandibular growth in Brazilian children with Class II malocclusion and normal occlusion during the growth stages determined by the cervical vertebrae maturation 13 Dental
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Table 3 :
Comparison between Class II and Normal Occlusion groups, for female and male genders, in the Initiation, Acceleration and Transition CVM stages, and t-test (p).

Conti ACCF, Fernandes TMF, Araújo PPB, Pinzan A -Cephalometric comparison of mandibular growth in Brazilian children with Class II malocclusion and normal occlusion during the growth stages determined by the cervical vertebrae maturation 14 Dental
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Silva FLBS, Conti ACCF, Fernandes TMF, Araújo PPB, Pinzan A -Cephalometric comparison of mandibular growth in Brazilian children with Class II malocclusion and normal occlusion during the growth stages determined by the cervical vertebrae maturation 16 Dental
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Silva FLBS, Conti ACCF, Fernandes TMF, Araújo PPB, Pinzan A -Cephalometric comparison of mandibular growth in Brazilian children with Class II malocclusion and normal occlusion during the growth stages determined by the cervical vertebrae maturation 18 Dental
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Conti ACCF, Fernandes TMF, Araújo PPB, Pinzan A -Cephalometric comparison of mandibular growth in Brazilian children with Class II malocclusion and normal occlusion during the growth stages determined by the cervical vertebrae maturation 19 Dental
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